Soil: dependence

how society depends on soil

The cultivation of soil has enabled humans
to build empires and to progress to what we are today. But the world's
population is now increasing so rapidly that within 40 years, enough food
and energy needs to be found to accommodate nearly twice the number of
people living today. Optimism of twenty years ago has turned into concern.
Will we be able to make it? Here are some issues that will sharpen your
mind.

From hunter-gatherer to the modern agro-economic society, has taken
thousands of years but now humankind is faced with a very sudden increase
in its population, demanding new and smarter methods to sustain it. Humans
depend on soil and what it produces, for food, energy and miscellaneous
materials.

One third of the world's population is either undernourished because
not enough food is available, or overweight because food is plentiful.
A separate section will be devoted to proper feeding, but here is an introduction
to our basic needs.

Soil forms very slowly over a period of tens of thousands of years,
too slow to be noticed, reason why ancient agriculture has erased itself
in many places. Unlike any other form of economic activity, agriculture
must satisfy several criteria of sustainability in order to survive.

History

As
can be seen from the diagram, the human race has grown very suddenly at
an enormously accelerating rate after the year 1850 when the industrial
revolution began. Before it, the human population curve stayed steady at
500 million people since year zero, with a few dips caused by plagues.
From 10,000 years ago, there have been several rapid increases, each co-inciding
with an invention of some kind. The number of births and deaths per 1000
population stayed close to 40. But since the 1850s, the death rate declined
suddenly, and even more steeply since 1950. The gap between births and
deaths has led to the rapid increase in world population. Since about 1950
the birth rate had been declining suddenly but not as fast as the decline
in deaths.

Before 8000BC, there must have been some 5 million people in the entire
world, just at the end of the first stone age and the beginning of the
new stone age, which brought the very first beginnings of agriculture.
Before that, humans had to forage and gather food by walking long distances.
This kind of life could sustain a family of ten on an area of ten square
km. Large aggregations of people were simply not possible.

Even
while foraging, people did influence their environment by removing noxious
or useless plant species and helping advantageous ones. This meddling with
nature, eventually led to agriculture.
Agriculture went through pastoralism, by which herds of grazing animals
were herded over natural pastures, to shifting-farming and finally to traditional
farming. Farming required people to stay in one place and farm the earth
there, now and then supplemented by hunting and fishing. The new ways of
farming, made possible by the invention of the plough and domesticated
animals for ploughing and transport, also enabled the development of better
tools and weapons from metals. Industry, boats and trade developed.

From 3000BC to 2000BC was the
bronze age, followed by the iron age to about 500AD. During that time several
civilisations rose and fell, like Babylon, Egypt, Greece, Rome. Although
scientists today differ about the causes of the rise and fall of these
civilisations, Plato clearly identified the demise of the Greek power from
loss of the land, not being able to sustain its civilisation any longer:

"The consequence is, that in comparison of what
[Attica, central Greece] then was, there are remaining only the bones of
the wasted body, as they may be called, as in the case of small islands,
all richer and softer parts of the soil having fallen away, and the mere
skeleton of the land being left". Plato, 360BC.

In the middle ages that followed, major inventions were made, that eventually
led to the green revolution of today. Although medical technology enabled
people to live longer, it was farming and the use of soil for production,
that enabled human societies to become denser. Here is a summary of the
revolutions in food collecting. Note that hunting and fishing always supplemented
nutrition, but those who mastered agriculture, also amassed wealth and
power, leaving hunter-gatherer-fisher societies far behind.

Foraging: 0.5 people per square km. Nomadic people move large distances,
eating what they encounter.

Pastoralism: 5 people per square km. Nomadic people move with their
herds.

Shifting farming: 50 people per square km. People burn forest, plant
until fertility is lost, then move on.

Traditional farming: 500 people per square km. People stay on the
land, with their herds. They maintain a mix of pasture, arable land, gardens
and stabled animals. Animal wastes are cycled onto the land.

Modern farming: 1500-2000 people per square km. Assisted by the
enormous power of fossil fuel, farming is highly mechanised, requiring
little labour. Lavish use is made of fertilisers. Agricultural products
are shipped vast distances.

Genetic engineering: ?

The question mark in the last sentence indicates that we've reached an
era of uncertainty. We will not be able to improve farming tenfold again,
because we are reaching the limits of agricultural production in many ways.
The question has now become whether the world population can be constrained
and whether we can produce enough food just in time. Also whether the future
situation can be maintained sustainably. Most of this section on soil will
be devoted to understanding our limits.
The way an ecosystem reacts to a population exceeding its limits, is
by rather sudden collapse. As the green curve in above diagram shows, it
is quite possible for the world's population to collapse and probably much
more rapidly than shown. The brown curve for area of cropland, may collapse
too. Most ecologists now agree that without the help of fossil fuel, the
world cannot sustain more than half today's population.

The connection between agriculture and civilisation is not a trivial
one. In order to be able to maintain a bureaucracy, an army, a legislature
(the law), engineers, artisans, and so on, the farmers must produce not
only enough food for themselves, but also enough to spare for those
who do not produce their own. The more efficient farming, the richer and
stronger is society. This has unfortunately, over the ages, also depressed
farm wages, for the less one needs to pay for food, the more is left over
to spend on culture. When farmers are put under unnecessary strain,
they will farm to survive, taking ecological shortcuts that will inevitably
lead to ecological disaster. It is society's responsibility to avoid this
happening. Society would indeed be foolish in not assisting its farming
communities.

Ironically, on the scale of farming success, the extremes on either
end are hard to control: at the lower end, subsistence farming will
exceed nature's carrying capacity in order to survive. Farming for greed
at the other end of the scale, will have the resources and the motivation
to exceed nature's carrying capacity for short-term profits. In the middle,
where farming is just profitable, will it be possible to farm sustainably.

Reasons for concern

In the population growth diagram above, a solid brown curve is also shown,
representing the amount of crop land (excluding forest and pasture), increasing
from 0.8 to 1.6 billion hectare (Gha) in the time span of 100 years. It
is obvious that this curve is flattening off, not keeping pace at all with
population. It not only shows how much has been achieved in improving agricultural
productivity, but also that no more land is available to increase production.
In fact, much good agricultural land has been lost to optimistic farming
practices (overfertilising, irrigation, desertification, soil loss), while
large corporations appear in control of seeds, fertiliser and pesticides.
The world's cropland now stands at 1.5 Gha, after losing 0.43 Gha already,
and reaching its limits. By comparison, the surface area of all ice-free
land = 13.3Gha; the whole world 51Gha.

As can be deduced from the summary of advantages and disadvantages of
the green revolution, it is not at all certain that it is sustainable and
that it will deliver what is needed for 11 billion people. For instance,
the amount of cereals (wheat, rice, etc.) per person has not increased
since 1975, staying steady (even decreasing) at 350 kg/yr each, despite
the fact that grain yields have been increasing from 1.5 tonne/ha to 2.5
in the same period. Simply by more people having to share the same land,
the available cropland per capita was 0.3 ha in 1986 and is now 0.23 ha,
decreasing further to 0.15 ha by 2050. It is estimated that 0.5 ha per
person will just give an adequate amount of food and cooking fuel (Americans
have 0.68 ha each). Not knowing that the world's arable soils would become
so scarce, people have built their cities over the most valuable and productive
soils. In the USA 0.8 ha per person has been paved by cities and roads.

Modern agriculture is characterised by large
industrialised monocultures. Where pigs or broilers (young chickens) are
reared, they are reared in closed confinement in very large numbers, producing
large amounts of wastes that are difficult to recycle because of transport
costs. Large fields in monoculture are very sensitive to pests, requiring
excessive amounts of chemical pesticides. There's little scope for land
cycling (alternating crops), green manuring (alternating fertility crops
like legumes) and fallowing (leaving land unused). To reach the highest
possible yields (and profit), even small losses to birds, mice, insects,
are fought with chemical overkill. Pesticides and fertiliser leach into
groundwater and aquifers and into streams and the ocean, where they cause
measurable harm. A safe limit of 50ppm (parts per million) nitrate is in
place for our aquifers, but this amount kills marine fish and other organisms
in a marine aquarium. In many cropland areas, such as in Holland, groundwater
is polluted by concentrations of nitrates exceeding 100ppm. The amount
of nitrate raining down from the sky, in many places in Europe and the
USA, exceeds the equivalent of 100kg/ha fertiliser application. It fertilises
dunes and changes their ecology.

For optimal productivity, farm animals are fed growth hormones and antibiotics,
which end up in their meat, causing endocrine disruption in people who
eat a lot of it (excessive growth, obesity and early start of menstruation
in girls are known to have been caused by better diets, but may be linked
to the use of hormones in food as well).

Although much environmental harm has been caused already, the good news
is that both consumers and farmers are becoming more aware and more cautious
in embracing new technologies for profit only. We are obviously entering
an era where we need to be smarter and eat smarter.

Food requirements

Of the 6 billion people on Earth, 1 billion is seriously underfed, suffering
reduced life spans, whereas an equal number is overfed, also reducing their
life expectancies considerably. The human body is capable of surviving
happily somewhere in between these extremes. The ability of our fat cells
to store fat for times of need, has served us well in the course of evolution,
but since food has become so readily available in fast food outlets and
elsewhere, many people fall victim to the seduction of eating too much
and too much fat. How we spend our energy, and how to eat will be treated
in its own section, but here we'll look at the ecological aspects.

The main food components people need are (with daily pure amounts per
kg body weight):

water to maintain respiration, perspiration and urination.

carbohydrates and fat for energy. Depending on work 30-60 kcal/kg/day.

fibre as roughage for smooth digestion and substrate for digestive bacteria

minerals to maintain mineral concentrations in body fluids

vitamins and trace minerals for health

Plants can provide all of the above, making life as a vegetarian perfectly
possible, although with some difficulty. Particularly children under 3
years, need animal proteins (milk, eggs, 2g/kg/day). A problem with protein
is that mammals, including humans, are unable to make 9 essential amino
acids (and one more very early in life). Although animal meat provides
these in the right ratios, plant proteins usually do not. It requires vegetarians
to eat more plant protein than the required daily amount (RDA).

As can be seen from the above range in energy expenditures, the amount
of food needed also varies. It would indeed be very difficult or impossible
to predict the amount of food needed to feed the world, by starting from
these figures. The best estimate we can make, is by starting from the situation
as it is today, taking account of a doubled population and 50 percent extra
for more equality in the distribution of wealth. It adds up to being able
to provide 3 times more than today, which, as we will see, is not achieved
easily and sustainably.

From the amount of energy spent in an office job, it is difficult to
compose a diet that does not overfeed, yet provides everything one needs.
A few greasy chips, a bar of chocolate and similar delights, can easily
tip the scale, resulting in preventable disease. The more energy one spends,
the easier it is to eat healthily. It is not surprising then, that many
diseases are linked to poor eating habits, or rather poor exercising habits,
diseases that were uncommon before the automobile became commonplace:

Health
problems that could be avoided by diet change and exercise

disease or condition

% of casespreventable

what to do

cancer

30-40

eat more fruits and vegetables,
less fat and exercise more

coronary heart disease

17-25

eat less fat and exercise
more

childhood blindness

25-50

eat more vitamin A; more
vegetables rich in micro-nutrients

mental retardation

33-43

use iodised salt.

adult-onset diabetes

64-74

eat less fat and exercise
more.

the above shows that one cannot be healthy
without exercise!

Meat or vegetarian?

Agriculture
does not escape the principles of physics and ecology. One of these is
the food or energy pyramid, shown here. Solar energy is converted by grass
(primary producer) and is eaten by grazers (primary consumers). They use
the food for growing , moving and living. But only a small amount is used
for growing, usually between 5 and 20%. It is called the conversion efficiency
or conversion rate. For quick ecological estimates, often the figure 10
is used, meaning that 10kg food is required to grow one kg. It corresponds
to 10% efficiency.
If wheat was grown instead of grass, humans could eat the wheat direct,
and thus attain a ten times better usage of the soil. So if people went
vegetarian, we would get up to ten times more food, solving the world's
food shortage in one step. We will see that this is not that simple.

In
studying how animals spend their energy, Kleiber discovered that there
is a fixed relationship between body weight and basal metabolic rate, the
energy spent when at rest. In mammals, this energy is mainly used for staying
warm, but part of it also for breathing and pumping the blood round. It
is known that the weight of an animal is related to its length to the power
of three and its surface area likewise to the power of two. So, bigger
animals need to spend more energy to stay warm, but proportionally less
than small ones. A human baby spends proportionally more energy staying
warm, than an adult. If heat loss were the only expenditure, Kleiber's
law should be:

BMR = 3.4 x weight0.67 rather than BMR
= 3.4 x weight0.75 , but this is a fine detail.

It is important to know that some farm animals spend more of their energy
growing than living, and pigs and broilers appear to be very effective
at gaining body mass, particularly when young. Like humans, mature animals
no longer grow. They spend their energies in living and reproducing instead.
If one wants to rear lots of young animals for the production of meat,
it can only be a species that reproduces profusely, like pigs (1-15 per
litter, 3 litters/year), chickens (200-300 eggs/ year), rabbits (?). The
traditional grassland animals like cattle, sheep, goat, deer are most unsuitable.

Kept in confinement, animals will, out of necessity, spend little energy
in moving around. So the conversion rates are optimal. When also fed the
right diet, their conversion rates can be astounding:
Piglets are weaned after 3-5 weeks, reach slaughter weights of 90-100
kg in 100-160 days. It means that many pigs are now marketed in less than
5 months after birth. Weaned piglets start with a conversion rate of 1.3,
rising to 3.5 at 90 kg body weight.
Chicken broilers do even better, perhaps because of their higher body
temperature and being non-mammals. In 9 weeks they reach 2-3 kg for conversion
rates starting at 1.5 and ending at 2.0. (Ducks 2.5-2.9 and turkeys 2.5-3.2).
Compare these conversion rates with cattle (8-19), eggs (2-3), fish
(1.4-2), milk (1.0). The table below , compares efficiencies of animal
food production:

(*) per litre of milk. Multiply
by 4 to compare with other columns.After Vaclav Smil: Feeding
the world. 2000.

From this table we can see that food production from milk, eggs, chicken
and pork is far more efficient than from grazing animals like sheep and
cattle, but fish are most productive. In Asia and china, fish aquaculture
in freshwater ponds has almost reached the same volume as all ocean fisheries,
supplying well over 15% of all dietary protein. Carp ponds can produce
100-300kg/ha (50kg/ha protein) without any fertilisation or feeding, but
with extra feeding, polycultures of multiple fish species yield 15-40t/ha.
Compare this with 80t/ha for vegetables and 20-30t/ha for fruits,
all yielding much less protein per ha.

Polyculture
of freshwater fish species

Silver carp(Hypophthalmichthys
molitrix) lives near the surface, feeding on phytoplankton.Bighead carp(Aristichthys
nobilis) occupies the middle layers, feeding omnivorously on plankton.Grass carp(Ctenopharyngodon
idella) is a herbivore, feeding on aquatic plants and organic waste.Common carp(Cyprinus
carpio) lives on the bottom and feeds from detritus.

Source: Vaclav Smil: Feeding
the world. 2000.

With milk, eggs, chicken and pork being such efficient protein converters,
the world would not be helped very much by exclusively vegetarian diets.
Besides, much of their food is considered unsuitable for humans, such as
fish meal made from by-catches, and crop wastes. Whereas fish ponds and
milk cows may compete with good cropland, beef cattle and sheep roam on
grasslands that are not suitable for cropping, so they remain efficient
sources of meat, hides and wool. So, neither cropland nor harvest can be
saved by shifting our appetites to vegetable matter.

Why do we need soil?

Why
would we need soil in the first place? Can't we rely more on using hydroponics
to feed the world? Hydroponic cultivation is the pinnacle of technological
cropping, where most of the climatic conditions are controlled: temperature,
CO2 concentration, moisture, nutrient levels. Usually done in temperate
climates inside modern glasshouses, this method of high intensity cropping
has found widespread use.
In the glasshouse the temperature is kept under control. Often carbon
dioxide gas is added to the atmosphere inside. Chemical sprays can easily
be contained inside a closed environment, resulting in savings. But best
of all is the controlled application of nutrients, while water is copiously
available because it is circulated.

Hydroponics has taken the world by storm for the cultivation of specialty
crops such as high quality and highly priced vegetables and fruits. Hydroponic
cultivation requires a flat, slightly sloping floor and a capital-intensive
structure. In most cases the energy content of the product is less than
the energy put into the process. It is energy inefficient and unsuitable
for the staple food of the world like cereals, tubers and pulses (beans),
or for slow growing crops like tea or rubber. But it has proved that soil
is not strictly needed for growing food. So what advantages does cropping
in the open soil offer?

The idea of agriculture is to convert solar energy into food and products
necessary for people, with the least amount of meddling (time, energy,
fertiliser, chemicals). It ought to be like using the forces of nature
to produce what we need. Since the only living organisms able to convert
sunlight into something useful, are plants, agriculture will mainly be
concerned with growing plants. Over the eons of time, plants and soil have
been together, the one influencing the other. They form the most important
part of the terrestrial ecosystem. Soils do naturally what has to be done
artificially in hydroponics, like:

a deep structure with low density and enough air space

enables plants to root in, providing a hold-fast

provides oxygen to roots

retains moisture

sponges up and drains excessive moisture

soil micro organisms to assist its functioning

to retain and exchange nutrients

to cycle nutrients

to transport moisture, nutrients, energy

a cohesive structure that retains its potential

minimises leaching losses downward

minimises erosion and water run-off

stabilises acidity levels (pH)

By understanding how soil works, we will be able to farm in an ecologically
friendly way that will be sustainable forever.

SustainabilityUnlike any other economic activity or commercial business, farming
must satisfy a number of harsh sustainability criteria. It also operates
under high external risks and uncertainty (weather, disaster). For society's
own sake, and in order to enable farming to become more productive, some
help is needed to insure risk, provide capital and to look after the precious
and vulnerable resource, the soil. Society does not know of any asset that
is (or should be) as long-lived as soil. Which building, bridge, dam will
have a life of over 10,000 years? How much is soil worth? How much would
it cost to make a hectare of soil by artificial means? We don't know the
answer. Is it important? How important is food? What comes first, fuel
or food? Hypothetical questions perhaps, but they dig at the roots of our
attitude to soil and agriculture. It requires us to think outside the frame,
outside present economic thinking.

Agricultural
sustainability

be profitable

be energy efficient

retain soil quantity

improve soil quality

retain water quality

Before everything else, farming, like any other business, needs to be
profitable in order to survive. That means that dollars earned must exceed
dollars spent. Unlike most other businesses, farming operates under the
vagaries of weather and climate. Unlike most other open air businesses,
farms are hit hard by natural disasters, from frost and deluge to earthquakes.
These are unpredictable and hit hard at a community's resilience, their
damage erasing many years of profits. Farmers are extremely exposed to
fluctuating and usually unfavourable market prices. In small markets, these
are unduly influenced and controlled by the big buyers, resulting in underpayment
for their produce. The farm cycle is controlled by the seasons, leaving
little room for planning, marketing and stockpiling. Farmers live in remote
areas, incurring high costs for their daily needs and the education of
their children. The list goes on.

Farmers derive their resilience from nature's ability to repair, from
being able to postpone costs a few years. But loan repayments do not fit
into this category, hence their need for assistance in financing.

Above all else, farmers need to look
after the soil that enables them to live, a soil 'borrowed from our children',
a soil that must be bequeathed to them 'in as good or better state as we
received'. With a renewal rate of tens of thousands of years and erosion
risks far too high, this is no easy assignment.

The American Society of Agronomy defined agricultural sustainability
as summarised in the box on right. They go as far as saying that it should
enhance environmental quality, the resource (soil) and the quality of life
for all (not just the farmer), an even tougher mission. Mr Rutan has added
another constraint, that of substituting biological technology for chemical
technology. (Is any farmer reading this?)

Large-scale farming is constrained too by having to be energy-efficient,
which means that the amount of energy used must always be less than the
amount of energy in the product. Many businesses exist, indeed the majority,
where this is not true (all services, the bureaucracy, army, police and
so on). Farmers use their tractor, which cost energy to make and fuel to
run. They use fertilisers made or modified by factories and transported
to the field. They use chemicals that were produced with large amounts
of energy from fossil fuel. The list goes on.
As fossil fuel becomes more expensive, the drive behind farming efficiency
using high yielding crops, will bend towards higher fuel efficiency (less
fertiliser, chemicals, tilling, transport). So the question becomes 'how
little fuel?' rather than 'how much yield?'.

Most of the chapters in this section on soil will focus on its sustainable
use, and the understanding necessary to do so.